Holley 2300 questions

Discussion in 'General IH Tech' started by RinTX, Aug 18, 2019.


  1. RinTX

    RinTX High Wheeler

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    I am redoing a rebuild on a Holley 2300 which is/was on a 304 original to a 1973 1010 Travelall. This second rebuild is due to something not quite right on acceleration, also a “stumble” steady state at 50-60 mph.
    The first rebuild kit came with a 2 stage power valve. What I removed during the first rebuild was a single stage. No markings on either of those.
    The power valve in this kit is a single stage marked 10.5.
    1. I was surprised the rebuild kit does not include replacement jets. Maybe this is normal. The jets in there are marked 51. Are replacement jets something I have to get on my own? Are 51 “correct”? Should I give something different a try? I live in Fort Worth TX. About 600ft elevation. Should be mostly local driving.
    2. On the accel cam. I thought I read on here once to get a accel cam kit and try the blue cam on the #2 hole. Is that correct?

    Thanks in advance for the help!
     
  2. Dana Strong

    Dana Strong Dreams of Cub Cadets

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    What was original and is correct depends on the List Number of that carb. which you haven't provided. With that, I could probably give you the part number of the jets, and of the original Power Valve. My understanding is that the two-stage valves have gotten hard to find.
    As an aside, I once rebuilt my List 4574 using an IH supplied kit which I later learned was wrong and contained a single stage Power Valve. When I got to higher elevations in the Sierra Nevadas on a trip later, I had power and backfiring problems which were caused by incorrect operation of that valve. I put the old one back in, once home, and didn't have the problem again.
     
  3. scoutboy74

    scoutboy74 Lives in an IH Dealership

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    No jets in rebuild kits. That's always a separate purchase.
     
  4. RinTX

    RinTX High Wheeler

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    Dana,
    The list is 6386. The 304 is original. The 2300 was installed ?? and on the vehicle when I bought it.
    26A83D3D-43AE-4661-A7D6-4FFA947086D4.jpeg
     
  5. Dana Strong

    Dana Strong Dreams of Cub Cadets

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    My Holley book shows that unit as having been installed on 1972 IH vehicles with 345 engines, auto transmissions and w/ AC. It has three versions: R-6386A, R-6386-1 and R-6386-2, the last using a different gasket set; all have an auto choke and, according to the 'correct' diagram, use idle adjusting screws going into the sides of the metering block. Your unit seems to be the first version. The first two use Master rebuild kit 85R-3502-S while the last uses 85R-4753. All use main jets 22R-40-51 and power valve 25R-475A-15. [Mine (R-4574) uses 25R-475A-13 and has the idle screws in the back of the throttle body assembly].

    FWIW, the interchange list on the following ad says it's equivalent to the Holley 25R-475A-15 power valve, but I'd do more research before believing that, particularly because it also lists 25R-475A-13 as being the same. Is it even two stage?
    https://www.ebay.com/itm/NEW-CARBUR...653308&hash=item591de42fd5:g:GZ4AAOSwxFVcTpmQ
     
    Last edited: Aug 19, 2019
  6. Greg R

    Greg R Dreams of Cub Cadets

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    Jets do not wear out, and they are vehicle/engine and fuel specific ; so no jets in any kits. Auto parts such as Napa or O'Reillys will have a Holley section for jets, metering block and fuel bowl gaskets, and linkage parts for tuning and dialing in the carburetors. Also, throttle body gaskets have to match perzactly, dead-on exact. Many kits will have 2 or 3 body to throttle plate gaskets, and one will look close, and one fits. Attention to this detail will save troubleshooting vacuum, idle, and cruise problems so pick the one that fits or match to the original.

    Have you checked the fuel bowl level? Post some vacuum readings. You really can't a tune or trouble shoot a carburetor properly without a vacuum gauge.
     
  7. RinTX

    RinTX High Wheeler

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    Thanks for the replies.
    Dana - the idle mixture screws are on the back of the metering block on this one.
    Not a great pic but this shows them...
    8099143C-CC9C-4691-968A-E18C774F28C4.jpeg
    The kit I’m currently using I got from IHPA.
    Greg - I will pay careful attention to the gasket selection and making sure they line up with all the passages.
    Should I just use the 51 jets?
    What about the accel pump cam?

    Edit for additional information- I double checked the fuel level in the bowl before I removed the carb from the vehicle yesterday.
     
    Last edited: Aug 19, 2019
  8. jeff campbell

    jeff campbell Lives in an IH Dealership

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    There are carb adjustment specs in the service manual also.
     
  9. Dana Strong

    Dana Strong Dreams of Cub Cadets

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    That is the throttle body and it looks like the one on my R-4574, indicating the Holley drawing was somewhat generic for many List Numbers.
    But...The metering block sits between the fuel bowl and the Main Body, above the Throttle Body. I put my book away, or I'd list its number here too.
    I can't answer the pump linkage question (easy to test your assumption of a different one needed), but would think the high speed stumble is likely due to the wrong power valve.
    Any chance you still have the original one, from before the rebuild?
     
  10. RinTX

    RinTX High Wheeler

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    Dana - I do have the “original” power valve I took out from the first rebuild. It is a single stage. No numbers visible on it. It’s not any good. Seems to be “stuck”. This vehicle sat for at least 16 years before I got it.
    I am hopeful that the power valve change back to a single stage will improve things.
    I don’t see any adjusting screws going into the side of the metering block. Only idle adjusting screws are in the throttle body.

    Still hoping someone could chime in about the jets...
     
  11. Dana Strong

    Dana Strong Dreams of Cub Cadets

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    I'm confused; the original valve was a two-stage, based on the numbers I gave in Post 5. I'd also say, based on the original jet number, that #51 is the original size (but based on 'real' gasoline). One size larger (numerically smaller, #50) may be better, particularly if the correct power valve isn't available, and it may stop the HS stumble. Greg may know better.
     
  12. scoutboy74

    scoutboy74 Lives in an IH Dealership

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    The larger the number, the larger the orifice. A smaller number would thus be more lean.
     
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  13. Greg R

    Greg R Dreams of Cub Cadets

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    Power valves don't kick in until full acceleration or WOT. In high speed cruise mode manifold vacuum should be too high to allow the power valve to operate. I am thinking, only thinking, you may have some run-lean conditions or a vacuum leak somewhere.

    As to jetting, it doesn't hurt to go up a couple of sizes. Jet numbers are directly related to orifice diameter but they really don't affect performance until you go up or down at least two sizes from your base ones. It has to do with the relation of orifice area vs. actual fuel flow and that gets into temperature/density etc. The practical side of changing jets is in 2 number increments gives you the best noticeable response. With today's alcohol laced fuels, fattening the jets helps a lot with drivability though at some expense with mileage.

    I highly recommend a book to help you with Holley carbs. Any title with Mike Urich as an author, or one of them, is the one to get. His knowledge and readability make them fun to learn about Holley set ups.

    I won't recommend changing jets, or PVs until we get some base readings. Fattening jets for a leak caused lean condition is just a band-aid and not good for the motor in the long run. You have to know where you are to know where you want to be.
     
    Last edited: Aug 19, 2019
  14. Dana Strong

    Dana Strong Dreams of Cub Cadets

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    I thought they were like number drills...thanks for correcting.
     
  15. RinTX

    RinTX High Wheeler

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  16. Bill Bennett

    Bill Bennett High Wheeler

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    In my carb book by Mike Urich, based on the 50cc pump, the accelerator pump chart indicates the White cam in the #1 position provides 17cc. The Blue cam in #1 position provides 18cc. The White cam in #2 position provides 19.5cc. The Blue cam in #2 position provides 20cc.
    The Holley carb that was stock was the 275 CFM model and had the 30cc accelerator pump. Same 30cc capacity pump with the White cam is used on the 350 CFM Holley 2300 carb. The indicated size of pump shot is based on 10 strokes of the 50cc pump.
    If it takes 10 strokes of the accelerator pump to go from 17cc using the White cam in the #1 position to 18cc using the Blue cam, that's 1/10cc difference between the different cams per stroke. Moving the White cam to the #2 position increases the shot to 19.5 cc, an increase of 1.5 cc over the #1 position. The Blue cam in #2 position gives 20cc or 1/2cc more than the white cam. Again, that is based on 10 strokes.
    Another point to consider is the size of the accelerator pump discharge nozzle. They are available in different sizes and can be changed to effect the length of time it takes to allow the fuel from the accelerator pump to be discharged into the airflow of the carb.
     
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  17. RinTX

    RinTX High Wheeler

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    So the old gasket and the new gasket cover these holes...
    A071AA8D-4D59-41B9-B64C-D50C84534208.jpeg BC63990E-48BF-40E5-B4FE-716A4FDE8672.jpeg
    I circled them in yellow on the second picture.
    Should they be covered?
     
  18. jeff campbell

    jeff campbell Lives in an IH Dealership

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    If those are dead end holes, id say yes, cover them. ? Spray some carb cleaner thru them with the straw or light compressed air and see what happens ! ?
     
  19. jeff campbell

    jeff campbell Lives in an IH Dealership

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    20190820_105552.jpg 20190820_105543.jpg Hopefully within the hour I can have a answer for you. Will look on a few partial carbs I have and some loose gaskets. " they're covered ! Your good to go !
     
    Last edited: Aug 20, 2019
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  20. RinTX

    RinTX High Wheeler

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    Jeff - Thank you!
    It is so good to have that verification. Can’t thank you enough!
     
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